Conventionally, there has been proposed various seatbelt retractors that remove slack of a webbing in case of emergency such as vehicle collision and the like.
For instance, a seatbelt retractor includes a gas generating member, a cylinder portion, a rack that moves within the cylinder portion upon receipt of gas pressure, a pinion gear body that gets engaged with the rack and is capable of rotating integrally with the take-up drum, and a cover body that is mounted to an upper end portion of the cylinder and one of side plate portions of a housing so as to form a guiding path for the rack that moves from the upper end portion of the cylinder to protrude upwards.
In case of vehicle collision, a pretensioner mechanism portion activates, whereby a pinion gear body gets engaged with the rack, that is pressed and driven by the gas, and rotates. The pinion gear body capable of rotating integrally with the take-up drum includes a shaft portion that sticks out from one end thereof and rotatably supported and inserted in a shaft hole portion formed on the cover body forming a guide path for the rack. Further, at the other end of the pinion gear body, there is formed a clutch ring. An inner peripheral surface of the clutch ring includes a cam surface that holds plural clutch rollers provided on an outer peripheral portion of a conjunction body that is coupled with one end of the take-up drum. Further, the clutch ring is rotatably supported by the conjunction body.
An example of the above described seatbelt retractor is disclosed in Japanese Laid-open Patent Publication No. 2003-335217.
However, according to the seatbelt retractor disclosed in Japanese Laid-open Patent Publication No. 2003-335217, in case that the pinion gear body is rotated by the rack that is pushed and driven in response to activation of the pretensioner mechanism, the cam surface on the clutch ring in the pinion gear body tightly press the plural clutch rollers on the conjunction body. Thereby, the pinion gear body rotates integrally with the conjunction body. On that account, axis center of the clutch ring deviates with reference to that of the conjunction body due to deformation of the cam surface and the decentering of the pinion gear body causes driving loss of gas pressure, which causes problems such as deterioration in driving efficiency of the pretensioner mechanism.
Further, the rack's movement path constituting the pretensioner mechanism is comprised of the cylinder portion and the cover body, which is problematic in terms of structural complication. Further, the rack is moved by gas pressure and its movement is stopped when coming in contact with a first contact portion formed by carving on the side wall portion and a second contact portion formed at a lower end portion of the cover body. Therefore, the shape of the side wall portion constituting the housing and that of the cover body are made complicated, which is problematic in terms of increase in manufacturing cost. Accordingly, the pretensioner mechanism portion needs simpler configuration.
Further, since the rack's movement path constituting the pretensioner mechanism portion is comprised of the cylinder portion and the cover body, the configuration thereat is complicated and mounting operation to one side wall portions of the housing is complicated, as well. This is problematic. Therefore, the pretensioner mechanism portion needs simpler configuration and improvement on assemblage efficiency thereof.